Indexed columns are not used by the rising wave when joining on indexed columns in materialized views.
CREATE INDEX is only used to accelerate serving queries without 'CREATE MATERIALIZED VIEW'.
Unnamed indexes are automatically created and maintained inside the HashJoin operator for streaming queries.
Each join in a streaming query has its own unnamed index, and they are not shared.
An experimental feature called 'delta join' may utilize the same index in streaming queries, but it has limitations and may not perform as well as the exclusive unnamed index for each join operator.
